Project: H and New Age Codes
Project: H and New Age Codes H code: Over the last few years, Massó developed a 3D cartesian code, written in data parallel Fortran, using the original hyperbolic formulation of Bona and Masso (Physical Review Letters 68, 1097 (1992)). A special version of this code, known as H3expresso, has been used by various groups within the GC Alliance and elsewhere (e.g., SC95) as a sample code to drive the development of DAGH, HPF, and Parallel I/O libraries.New Age : Building on these efforts, Massó has developed a new 3D cartesian code based on the recent, generalized Bona-Massó formulation (BMSS for Bona, Masso, Seidel and Stela) hyperbolic formulation now allowing a large class of slicing conditions and an arbitrary shift. Check the project page on this new formulation for Numerical Relativity . This code presently allows a variety of evolution methods, including a MacCormack predictor corrector method on the standard evolution fields. It also takes full advantage of a number of methods applicable only to fully hyperbolic systems by evolving the complete set of eigenfields and applying special boundary conditions depending on the sign and value of the eigenvalue or characteristic velocity. The methods include second order upwind, Godunov, Van Leer and a minmod flux-limited TVD scheme that was shown to be extremely accurate for black hole evolutions in 1D, evolving a spherical black hole to beyond t=1000M, with a 2% error, without the use of apparent horizon conditions.
A fully general 3D shift vector is now being added, and the code will be tested using apparent horizon boundary conditions AHBC that borrow from the experience gained in 1D and 3D studies made over the last few years. Presently the code is undergoing tests and comparisons to the H3expresso and G codes on linear and nonlinear gravitational waves, Schwarzschild, and Misner black hole initial data, by the full group. 1D tests of this formalism applied to black holes with AHBC are also being used as a guide to the 3D project.
As the older H3expresso code was already used as a driver for the development of DAGH and the Adaptative Mesh Refinement Berger-Oliger support, the integration of the "New Age" code into the DAGH infrastructure is straightforward and is being carried out by Walker, Parashar, and Massó (see the project AMR). We are also working with Shalf and the Panda parallel I/O group to develop appropriate I/O routines for AMR data sets on parallel machines, which will be made available to the Alliance when they are ready. Presently, the New Age code runs efficiently, in parallel, on the Cornell SP-2, the PSC Cray C-90, the NCSA CM-5, Exemplar, and Power Challenge Array. Tests of the scaling properties of the code are underway, and we expect similar results to those obtained with the H3expresso code.
Check the New formulation for Numerical Relativity project page for theoretical background. See also the closely related AHBC and AMR projects.